New copolymer elastomers (Gaflex® ) derived from dimethylterephthalate (DMT), butanediol (B1D), butenediol (B2D) and polytetrahydrofuran are described. The materials are processable by conventional thermoplastic techniques and are available with a range of melt viscosities. The elastomers are tough, tear resistant, and perform over a broad temperature range. Appli cations are found in tubing, wire coating, sports equipment and bellows.